There have been demanded extensive developments of broad-band services such as dynamic image communication and picture image transmission or distribution, using fiber-optic communication capable of broad-band efficient data transmission or transfer. In electronics, for example, there have not yet been realized functional elements (active elements) equivalent to triode transistors, that is, optical function devices capable of controlling an optical signal directly with another optical signal.
Actually, therefore, an optical signal that has been transmitted at a high-speed is once converted into an electrical signal, which is subjected to data processing in an electronic circuitry, and the processed data signal is then reconverted into an optical signal to be transmitted. This incapability to achieve direct control of an optical signal with another optical signal has limited the efficiency of optical signal processing. If a data signal can be processed as received in the form of an optical signal, it is considered possible to perform parallel processing operations, which are expected to permit further reduction in the required signal processing time.
The present invention was made in the light of the background art described above. It is an object of the present invention to provide an optical function device which permits processing of an optical signal directly with another optical signal.